1. Technical Field Text
The present disclosure relates to medical devices. More particularly, the disclosure relates to a processing method and final product involving sequential biaxial straining of semi-crystalline tubes to prepare medical devices.
2. Background Information
Medical devices, such as stents and filters, need to withstand structural loads when placed within the vasculature of a patient. How well these devices withstand structural loads relates to both the mechanical properties of the material used to make the device and the device design.
Without sufficient mechanical properties, a medical device made from such a material may deform or fracture when placed in the vasculature and cause other later complications. A device should have sufficient strength to maintain its size and shape in vivo. Such devices may be formed from polymers.
Semi-crystalline polymers have crystalline domains and amorphous domains. Crystalline domains have highly ordered polymer chains. Contrastingly, amorphous domains may have a more random orientation of polymer chains. In order to improve the mechanical properties of semi-crystalline polymers, it is known to cause strain induced crystallinity. Strain induced crystallinity induces alignment of polymer chains in the direction of the strain. Strain induced crystallinity can improve mechanical properties in the direction of the strain, but there is a need for new methods to further improve mechanical properties in all directions.
Likewise, there is a need for further straining methods to adjust method steps as needed. For example, it may be advantageous to modify polymer chain orientation in multiple directions during the method. As such, there exists a need for further straining methods.